1. Field of the Invention
The present invention relates to a novel block copolymers having blocks formed from syndiotactic polystyrene and rubbery elastomeric (co)polymers such as styrene/butadiene or polybutadiene. More particularly, it pertains to the use of an extender such as oil or other low molecular weight components to highly extend syndiotactic polystyrene block-elastomeric block copolymers to produce soft compositions having high temperature resistance and processable mechanical properties.
2. Description of Prior Art
It has been known in the past to extend thermoplastic elastomers with petroleum base oils such as naphthenic, aromatic and paraffinic oils and other low weight molecular organic mataterials in order to reduce costs and to improve the elastomeric properties of certain of the thermoplastic elastomers. In U.S. Pat. No. 5.451,454, owned by the current assignee, a blend of a high-molecular weight block copolymer having a hard block and a soft block and a large volume of oily or low molecular weight material provides a composition having unique softness, adequate mechanical strength and damping properties useful in many industrial applications. The heat resistance of this composition was not adequate for higher temperature applications including many uses in automobiles and electrical appliances.
Japanese Patent Laid Open 93-320280 discloses block copolymers having an anionically polymerized polybutadiene or poly(butadiene/styrene) block and a syndiotactic polystyrene (sPS) block. However, neither this patent or any other prior art patent suggests the use of such a composition with a high oil content to obtain a soft material having a low Shore A hardness
It is extremely desirable to prepare a block copolymer composition having elastomeric characteristics, good mechanical strength, unique softness and utility in high temperature applications.